Structural highlights
Publication Abstract from PubMedWhile metal ion binding to naturally occurring L-amino acid proteins is well documented, understanding the impact of the opposite chirality (D) amino acids on the structure and stereochemistry of metals is in its infancy. We examine the effect of a D-configuration cysteine within a designed L-amino acid three-stranded coiled coil in order to enforce a precise coordination number on a metal center. The D-chirality does not alter the native fold, but the side-chain reorientation modifies the sterics of the metal binding pocket. L-Cys side-chains within the coiled-coil have previously been shown to rotate substantially from their preferred positions in the apo structure to create a binding site for a tetra-coordinate metal ion. However, here we show by x-ray crystallography that D-Cys side chains are preorganized with suitable geometry to bind such a ligand. This is confirmed by comparison of the Zn(II)Cl(CSL16DC)(3)(2) to the published Zn(II)(H(2)O)(GRAND-CSL12AL16LC)(3) .(1) Spectroscopic analysis indicates that the Cd(II) geometry observed using L-Cys ligands (a mixture of 3- and 4- coordinate Cd(II)) is altered to a single 4-coordinate specie when D-Cys is present. This work opens a new avenue for the control of metal site environment in man-made proteins, by simply altering the binding ligand with its mirror imaged D-configuration. Thus, use of D amino acids in a metal's coordination sphere promises to be a powerful tool for controlling the properties of future metalloproteins. D-Cysteine Ligands Control Metal Geometries within de Novo Designed Three-Stranded Coiled Coils.,Pecoraro VL, Ruckthong L, Peacock AF, Pascoe CE, Hemmingsen L, Stuckey JA Chemistry. 2017 Apr 6. doi: 10.1002/chem.201700660. PMID:28384393[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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